Image display apparatus

ABSTRACT

An image display apparatus ( 400 ) for displaying a series ( 102 ) of consecutive output images ( 110 - 114 ) which are based on a series ( 100 ) of consecutive input images ( 104 - 108 ), with the series ( 100 ) of consecutive input images ( 104 - 108 ) comprising a first image ( 108 ) and a second image ( 106 ), is arranged to split the images ( 104 - 108 ) of the series ( 100 ) of consecutive input images ( 104 - 108 ) in first parts ( 128 - 132 ) and second parts ( 116 - 120 ); and to display a first one ( 112 ) of the output images ( 110 - 114 ) which comprises a first block of pixels ( 136 ) corresponding to a first one ( 132 ) of the first parts ( 128 - 132 ) of the first input image ( 108 ) and a second block of pixels ( 124 ) corresponding to a first one ( 118 ) of the second parts ( 116 - 120 ) of the second input image ( 106 ).

The invention relates to an image display apparatus comprising:

-   -   means for receiving a video stream representing a series of        consecutive input images, with the series of consecutive input        images comprising a first image and a second image; and    -   a display device for displaying a series of consecutive output        images which are based on the series of consecutive input        images.

The invention further relates to a method of displaying a series ofconsecutive output images which are based on a series of consecutiveinput images, with the series of consecutive input images comprising afirst image and a second image.

The invention further relates to a TV comprising such an image displayapparatus.

In video broadcasting, subtitles are employed to convey textualinformation to the viewer. The subtitles accompany an audio/videobroadcast and provide supplemental information to the viewer that maynot be perceivable from the broadcast. Subtitles are frequently used,for example, to aid hearing impaired viewers by displaying the spokenlanguage recorded in the audio soundtrack as written language. Anotherexample, is where subtitles are displayed in different languages thanthe spoken language recorded in the audio soundtrack. In addition,subtitles may be employed to convey important information not related tothe subject matter of the corresponding audio/video broadcast. In thiscase, subtitles may represent late-breaking news, such as: emergencyinformation; sports scores, weather reports or information of the stockexchange. Frequently the information is provided by means of a banner.The textual information moves relative to the display screen of thedisplay apparatus. Typically the direction of the movement is in ahorizontal or vertical direction.

In television broadcasting or video reproduction, such as from a videotape or disk, the subtitles or banners are previously superimposed onthe broadcast and become part of the received images. Hence the displayof the information of the subtitles or banners is linked with thedisplay of the other video content. It is a disadvantage that in manycases the provided textual information of the subtitles or the banner isonly visible for a limited period of time.

It is an object of the invention to provide an image display apparatusof the kind described in the opening paragraph on which a spatial partof a received series of input images is visible for a relatively longperiod.

The object of the invention is achieved in that the image displayapparatus is arranged:

-   -   to split the consecutive input images into respective first        parts and respective second parts; and    -   to display a first one of the output images comprising a first        block of pixels corresponding to the first part of the first        input image and a second block of pixels corresponding to the        second part of the second input image.

If further output images also comprise the first one of the first partsof the first input image then it can be seen as if the correspondingpart of the display device is frozen. The other part of the displaydevice is updated on a regular base with consecutive second parts. Notethat it is known to freeze the entire display device. However in thiscase only a part of the display device is frozen while the other part isnot. The invention is advantageous in the case that the first parts ofthe received input images correspond to respective portions of a banner:it can be seen as if the movement of the banner is stopped. By doingthis the readability of the banner is enhanced. The invention is alsoadvantageous in the case that the first parts of the received inputimages correspond to subtitles. By freezing the corresponding part ofthe display device, the user of the image display apparatus has moretime to read, or reread the subtitle.

An embodiment of the image display apparatus according to the inventioncomprises user interface means to provide location information of thefirst parts to control splitting of the images of the series ofconsecutive input images. It is assumed that in a default display modeof the image display apparatus the entire display device is updated on aregular base. However if the received input images comprise distinctparts then it is advantageously to split the images in first parts andsecond parts and to control the display of the first parts independentlyof the second parts. Location information of the first parts relative tothe second parts is required in order to split the received inputimages. A first option is that the user of the image display apparatusprovides this information. E.g. by dragging a graphics box or bymanipulation of a graphics line being displayed on the display device asa kind of overlay. Automatic segmentation of the input images is anotheroption to determine the location information. Motion estimation is agood basis for this segmentation. Alternatively the location informationis provided by means of the broadcast.

An embodiment of the image display apparatus according to the inventioncomprises a first memory device for storage of the location information.The location information is relatively constant. By storing the locationinformation it is no longer required to determine or provide thelocation information again. Optionally multiple instances of thelocation information are stored as a presetting for the variousbroadcasting channels. In that case a user of the image displayapparatus might start the required display mode, i.e. partially frozendisplay mode, with one push of a button of the remote control.Optionally the image display apparatus automatically switches from adefault display mode in which the entire display device is updated on aregular base into the partially frozen display mode. This switchingmight be triggered by a “banner-event”, i.e. the presence of a banner isdetected.

An embodiment of the image display apparatus according to the inventioncomprises:

-   -   a motion estimation unit for estimating motion in the first        parts;    -   processing means to calculate a time period during which a        particular part of the banner moves from a first predetermined        location relative to the display device to a second        predetermined location relative to the display device; and    -   a selector to select a further one of the first parts of a        further input image, on basis of the time period.

An advantageous of this embodiment of the image display apparatus isthat it is arranged to remove redundancy in the first parts. First partsof consecutive input images comprise portions which are also comprisedby other first parts of the consecutive input images. This embodiment ofthe image display apparatus is arranged to create a set of first partsof the input images, of which the elements of the set have a minimum ofoverlap with each other, but which together comprise a maximum of theinformation conveyed by the banner. The elements of the set might bedisplayed automatically or on basis of a user input. Optionally thesefirst parts are stored in a second memory device. This enables browsingthrough the set of first parts.

An embodiment of the image display apparatus according to the inventioncomprises:

-   -   a character analyzer designed to search for textual information        in the first parts; and    -   a comparing unit for comparing parts of the textual information        with a predetermined string of characters.

This embodiment of the image display apparatus is arranged to search forspecific textual information in the first parts conveyed by a banner orsubtitle. When this textual information is detected then one of thefirst parts comprising this textual information is displayed on thedisplay device. An example of such a character analyzer is specified inU.S. Pat. No. 6,195,459.

It is a further object of the invention to provide a method of the kinddescribed in the opening paragraph with which a spatial part of areceived series of input images is visible for a relatively long period.

This object of the invention is achieved in that the method comprises:

-   -   a splitting step of splitting the consecutive input images into        respective first parts and respective second parts; and    -   a display step of displaying a first one of the output images        comprising a first block of pixels corresponding to the first        part of the first input image and a second block of pixels        corresponding to the second part of the second input image.

Modifications of the image display apparatus and variations thereof maycorrespond to modifications and variations thereof of the methoddescribed.

These and other aspects of the image display apparatus, of the TV and ofthe method according to the invention will become apparent from and willbe elucidated with respect to the implementations and embodimentsdescribed hereinafter and with reference to the accompanying drawings,wherein:

FIG. 1 schematically shows a series of input images and a series ofoutput images according to the invention;

FIG. 2 schematically shows an embodiment of the user interface for thecontrol of the splitting;

FIG. 3 schematically shows the relation between a banner and a series ofconsecutive input images;

FIG. 4 schematically shows an embodiment of the image display apparatus;

FIG. 5A shows a data-flow diagram; and

FIG. 5B shows an alternative data-flow diagram.

Corresponding reference numerals have same or like meaning in all of theFigs.

FIG. 1 schematically shows a series 100 of input images 104-108 and aseries 102 of output images 110-114 according to the invention. Theimages 104-114 represent a portion of a sport game. Besides that,textual information is provided in the lower parts 128-138 of the images104-114. The parts 116-126 of the images representing the portion of thesport game do not overlap with the lower parts 128-138 of the images. Afirst one 114 of the consecutive output images 110-114 comprises a firstpart 138 which corresponds to a first block of connected pixels 132 of afirst one 108 of the series of consecutive input images 104-108, and asecond part 126 which corresponds to a second block of connected pixels120 of the first one 108 of the series of consecutive input images104-108. A second one 112 of the consecutive output images 110-114comprises a first part 136 which also corresponds to a first block ofconnected pixels 132 of the first one 108 of the series of consecutiveinput images 104-108, and a second part 124 which corresponds to asecond block of connected pixels 118 of a second one 106 of the seriesof consecutive input images 104-108. A third one 110 of the consecutiveoutput images 110-114 comprises a first part 134 which also correspondsto a first block of connected pixels 132 of the first one 108 of theseries of consecutive input images 104-108, and a second part 122 whichcorresponds to a third block of connected pixels 116 of a third one 104of the series of consecutive input images 104-108. Hence, the outputimages 110-114 comprise blocks of pixels 134-138 which correspond to thesame first part 132 of one 108 of the input images 104-108.

FIG. 2 schematically shows an embodiment of the user interface for thecontrol of the splitting between a first part 138 and a second part 126of the output image 114. On the display device 406 a graphics line 200is drawn as an overlay of the output image 114. The user of the imagedisplay apparatus 400 can adapt the position of the line by means ofpushing a plus or minus button of the remote control of the imagedisplay apparatus 400. Such manipulation of the display can be achievedusing the facilities of the OSD (On Screen Display) features of thedisplay apparatus 400 and or other graphics features of the displayapparatus 400. The position of the line 200, corresponds to the locationinformation which is required to split the images 104-108 of the series100 of input images in first parts 128-132 and second parts 116-120.Optionally the position of the line 200 is stored in a memory device.Preferably multiple instances are stored, e.g. a first position forchannel 1, a second position for channel 2, etcetera.

FIG. 3 schematically shows the relation between a banner 300 and aseries 100 of consecutive input images 104-108. A banner 300 can be seenas a strip of information which moves relative to the display device406. In a default display mode of the image display apparatus on which abanner 300 is displayed the output images comprise overlapping parts ofthe banner 300. E.g. a first image comprises a first portion 302 of thebanner 300, a second image comprises a second portion 304 of the banner300, a third image comprises a third portion 306 of the banner 300,etcetera. These portions 302-320 partly overlap with each other. Howeverthere are pairs of portions which do not have overlap e.g. first portion302 and fifth portion 310. It can be seen from FIG. 3 that with acombination of non-overlapping portions, e.g. 302, 310, 312 and 320 theentire banner 300 can be represented. By selecting the appropriateimages of the series of input images a set of first parts of the inputimages can be created, of which the elements of the set have a minimumof overlap with each other, but which together comprise a maximum of theinformation conveyed by the banner 300. Optionally these parts arestored in a memory device 506. See FIG. 5B.

An approach of finding these first parts is based on estimating motion.Motion estimation can be performed by a standard motion estimation unit.A standard motion estimation unit might be the motion estimation unitwhich is known from the article “True-Motion Estimation with 3-DRecursive Search Block Matching” by G. de Haan et. al. in IEEETransactions on circuits and systems for video technology, vol.3, no.5,October 1993, pages 368-379. The motion estimation unit provides amotion vector field. This motion vector field has to be analyzed, onbasis of a motion model of constant translation to determined thevelocity of the banner. The velocity of the banner determines theoverlap between parts of consecutive images. With knowledge of thedimension of the display area of the banner 300 the number of images tobe skipped can be calculated. As a consequence only the first parts fromone out of N images have to be dealt with, e.g. stored or displayed.

FIG. 4 schematically shows an embodiment of the image display apparatus400 comprising:

-   -   receiving means 402 for receiving a signal representing input        images 104-108 to be processed. The signal may be a broadcast        signal received via an antenna or cable but may also be a signal        from a storage device like a VCR (Video Cassette Recorder) or        Digital Versatile Disk (DVD). The signal is provided at the        input connector 408. The receiving means 402 is arranged to be        tuned to a predetermined frequency band to extract the input        images 104-108 from the provided signal.    -   processing means 404 for making the output images 110-114 on        basis of the input images 104-108; The processing means        comprises memory devices 500 and 506,    -   display means for displaying the output images 110-114. This        display means is optional. The functionality can also deployed        by making use of a e.g. Set-top box. In that case the displaying        is done by a Television and other parts of the processing by        means the Set-top box.

FIG. 5A shows a data-flow diagram. In FIG. 5A a memory device 500 isdepicted which is logically divided in a first part 504 in which firstparts 128-132 of input images 104-108 are written 508 and a second part502 in which second parts 116-120 are written 506. To display an outputimage 110-114 the memory device is accessed for reading 512 theappropriate first 134-138 and for reading 510 the second parts 122-126.In default display mode of the image display apparatus 400 the frequencyof reading 512 first parts 134-138 and of reading 510 second parts122-126 for the output images 110-114 is equal with writing 508 firstparts 128-132 and writing 506 second parts 116-120. However in thepartially frozen display mode of the image display apparatus 400 thefrequency of writing 508 first parts 128-132 is zero, i.e. no updates ofthe portion 504 of the memory device 500 for storing first parts128-132. Hence the stored first part 132 is repeatedly read. Note thatin principle there is no need for storing second parts 116-120 becausethese are directly displayed. The required memory size depends on thefirst parts 128-132 only.

FIG. 5B shows an alternative data-flow diagram. A second memory device516 is available for storage of multiple first parts corresponding tonon-overlapping portions 302, 310, 312 and 320 of a banner 300. One ofthe first parts is selected and written 514 to the first part 504 of theother memory device 500. The selection can be based on a direct usercontrol: next first part. Alternatively the selection is based on amatch of textual information comprised by the selected first part and apredetermined character string.

It should be noted that the above-mentioned embodiments illustraterather than limit the invention and that those skilled in the art willbe able to design alternative embodiments without departing from thescope of the appended claims. In the claims, any reference signs placedbetween parentheses shall not be constructed as limiting the claim. Theword ‘comprising’ does not exclude the presence of elements or steps notlisted in a claim. The word “a” or “an” preceding an element does notexclude the presence of a plurality of such elements. The invention canbe implemented by means of hardware comprising several distinct elementsand by means of a suitable programmed computer. In the unit claimsenumerating several means, several of these means can be embodied by oneand the same item of hardware.

1. An image display apparatus (400) comprising: means (402) forreceiving a video stream representing a series (100) of consecutiveinput images (104-108), with the series (100) of consecutive inputimages comprising a first image (108) and a second image (106); and adisplay device (406) for displaying a series (102) of consecutive outputimages (110-114) which are based on the series (100) of consecutiveinput images (104-108), characterized in that the image displayapparatus (400) is arranged: to split the consecutive input images intorespective first parts (128-132) and respective second parts (116-120);and to display a first one (112) of the output images (110-114)comprising a first block of pixels (136) corresponding to the first part(132) of the first input image (108) and a second block of pixels (124)corresponding to the second part (118) of the second input image (106).2. An image display apparatus (400) as claimed in claim 1, characterizedin that the first parts (128-132) correspond to respective portions of abanner (300).
 3. An image display apparatus (400) as claimed in claim 1,characterized in that the first parts correspond to a subtitle.
 4. Animage display apparatus (400) as claimed in claim 1, characterized incomprising user interface means (200) to provide location information ofthe first parts (128-132) to control splitting of the images of theseries (100) of consecutive input images (104-108).
 5. An image displayapparatus (400) as claimed in claim 4, characterized in comprising afirst memory device for storage of the location information.
 6. An imagedisplay apparatus (400) as claimed in claim 2, characterized incomprising: a motion estimation unit for estimating motion in the firstparts (128-132); processing means to calculate a time period duringwhich a particular part of the banner moves from a first predeterminedlocation relative to the display device (406) to a second predeterminedlocation relative to the display device; and a selector to select afurther one (128) of the first parts (128-132) of a further input image(104), on basis of the time period.
 7. An image display apparatus (400)as claimed in claim 6, characterized in comprising a second memorydevice (516) for storing the further one (128) of the first parts(128-132).
 8. An image display apparatus (400) as claimed in claim 1,characterized in comprising: a character analyzer designed to search fortextual information in the first parts (128-132); and a comparing unitfor comparing parts of the textual information with a predeterminedstring of characters.
 9. A method of displaying a series (102) ofconsecutive output images (110-114) which are based on a series (100) ofconsecutive input images (104-108), with the series (100) of consecutiveinput images (104-108) comprising a first image (108) and a second image(106), characterized in that the method comprises: a splitting step ofsplitting the consecutive input images into respective first parts(128-132) and respective second parts (116-120); and a display step ofdisplaying a first one (112) of the output images (110-114) comprising afirst block of pixels (136) corresponding to the first part (132) of thefirst input image (108) and a second block of pixels (124) correspondingto the second part (118) of the second input image (106).
 10. TVcomprising an image display apparatus (400) according to claim 1.